NCERT Solution for Class 10 Science Chapter 9 Heredity and Evolution
How does the creation of variations in a species promote survival?
Variations occur due to sexual reproduction and also due to inaccurate copying of DNA. Depending on the nature of variations, different individuals would have different kinds of advantages. For example, bacteria variants which can withstand heat have better chances to survive in a heat wave non-variant bacteria having no capacity to tolerate heat wave. Thus, variations in a population of a species help in survival of a species.
How do Mendel’s experiments show that traits may be dominant or recessive?
The trait which appears in all the members of F1 generation and also in 75% numbers of F2 generation obtained by self fertilization of F1 generation is dominant character. The trait which does not appear in F generation but after self-fertilization of F1 generation, reappears in 25% of F2 generation is known as recessive.
How do Mendel’s experiments show that traits are inherited independently?
Mendel crossed pure breeding tall plants having round seeds with pure breeding short plants having wrinkled seeds. The plants of F1 generation were all tall with round seeds indicating that the traits of tallness and round seeds were dominant. Self breeding of F1 yielded plants with characters of 9 tall round seeded, 3 tall wrinkled seeded , 3 short round seeded and one short wrinkled seeded. Tall wrinkled seeded and short round seeded plants are new combinations which can develop only when the traits are inherited independently.
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